I would think it would be a rodent virus/parasite. It would spread by rodents, and be similar to rabies. Just like other animals with rabies it would cause us to attack any movement. It would co-react most of our brain functions and cause us to only want to feast on meat. Making us Carnivores. Would you think this is how it happened, and how would you survive it?

but thats diffrent see people would just be cannibals not zombies you have to be dead to be zombie other than that you'djust be a really sick cannibal so it dosen't really count in my book for a zombie outbreak